1. Field of the Invention
The present invention relates to a sensor in a wired or wireless sensor system for monitoring potentially dangerous or costly conditions such as, for example, smoke, temperature, water, gas and the like. It also relates to a portable monitoring unit for monitoring conditions present in a building, or complex.
2. Description of the Related Art
Maintaining and protecting a building or complex and its occupants is difficult and costly. Some conditions, such as fires, gas leaks, etc., are a danger to the occupants and the structure. Other malfunctions, such as water leaks in roofs, plumbing, etc., are not necessarily dangerous for the occupants, but can, nevertheless, cause considerable damage. In many cases, an adverse condition such as water leakage, fire, etc., is not detected in the early stages when the damage and/or danger is relatively small. This is particularly true of apartment complexes where there are many individual units and supervisory and/or maintenance personnel do not have unrestricted access to the apartments. When a fire or other dangerous condition develops, the occupant can be away from home, asleep, etc., and the fire alarm system can not signal an alarm in time to avoid major damage or loss of life.
Sensors can be used to detect such adverse conditions, but sensors present their own set of problems. For example, adding sensors, such as, for example, smoke detectors, water sensors, and the like in an existing structure can be prohibitively expensive due to the cost of installing wiring between the remote sensors and a centralized monitoring device used to monitor the sensors. Adding wiring to provide power to the sensors further increases the cost. Moreover, with regard to fire sensors, most fire departments will not allow automatic notification of the fire department based on the data from a smoke detector alone. Most fire departments require that a specific temperature rate-of-rise be detected before an automatic fire alarm system can notify the fire department. Unfortunately, detecting fire by temperature rate-of-rise generally means that the fire is not detected until it is too late to prevent major damage.
Compounding this problem, alarm systems do not provide actual measured data (e.g., measured smoke levels) to a remote monitoring panel. The typical fire alarm system is configured to detect a threshold level of smoke (or temperature) and trigger an alarm when the threshold is reached. Unfortunately, the threshold level must be placed relatively high to avoid false alarms and to allow for natural aging of components, and to allow for natural variations in the ambient environment. Setting the threshold to a relatively high level avoids false alarms, but reduces the effectiveness of the sensor and can unnecessarily put people and property at risk. Such a system is simple to operate but does not provide a sufficient “early warning” capability to allow supervisory personnel to respond to a fire in the very early stages. Moreover, even in a system with central or remote monitoring capability, someone must be present at all times at the monitoring site to see what is happening, increasing the cost of monitoring.